In the early 1950s, a huge hole was dug into the Cumbrian coast and lined with concrete. Roughly the length of three Olympic swimming pools and known as B30, it was built to hold skip loads of spent nuclear fuel. Those highly radioactive rods came from the 26 Magnox nuclear reactors that helped keep Britain's lights on between 1956 and 2015. When B30 was first put to work, it was designed to keep the fuel rods submerged for only three months before reprocessing work was carried out. But when 1970s miners' strikes shut down coal power stations and forced greater reliance on nuclear plants, more spent fuel than could be quickly reprocessed was generated.